I must create a system, or be enslaved by another man's. I will not reason and compare: my business is to create.

- William Blake

Sunday, December 11, 2016

Stacking advantage/disadvantage in D&D 5e

Like many people, I am fan of the advantage/disadvantage mechanic in D&D 5e (click here if you don't know how this works). So much, in fact, that I've added it (albeit in a modified form) to my own RPG.

What I don't particularly like is how ad/disad doesn't stack. I understand the reasoning - let us keep this simple - but the results are often unsatisfactory for me.

Fortunately, someone has already "fixed it" for me.

To understand why this is a problem for some people, let me paraphrase the author's description of the problem:

"I have higher ground, the enemy is blind, bound, prone, and I have a magical effect enhancing my attack!" ...But only one advantage is accounted for? 

Okay, I added "bound" and "prone" for effect, but you get the idea. In fact, this didn't quite happen to me, but what did happen was a bit worse - although less obvious.

The gist of it is that I had built a character with a special strength against a certain enemy - my nemesis, so to speak. When I finally confronted him, I immediately used some power to give me advantage (although I don't remember which), since he was a "final boss" of sorts.

But I had info on my enemy. I had studied his habits, weaknesses, etc., and so when he attacked I used his weaknesses against him. It was an epic moment when he fell for my trap! And them the GM said.... "You have advantage to attack him for the rest of the combat"!

Which means: nothing.

You see, the GM gave me the opportunity to try my plan and decided that it had succeeded; he gave me advantage not to mess with me, but because he didn't realize I already had it. But even if he did, what else would he do? This is how D&D 5e works, RAW: if the player comes up with a clever tactic or puts himself in an advantageous situation, etc, he gets advantage.

I won't get too deep into the "why four advantages shouldn't be negated by one disadvantage". Four advantages and one disadvantage should mean three advantages. This is just common sense to me, but you might prefer to play RAW.

Anyway, the link above has a couple of fine solutions for the problem.

The first one is obvious: roll more dice. That works well enough, and although it messes with the probability of getting a critical, I don't think the Champion will suddenly become overpowered because of that.

But I like to avoid both messing with the game's assumption about critical AND rolling dice pools, which don't quite fit the way I play D&D.

The second solution is also good: +1 for each advantage after the first.

I have very a similar one, that I find a bit easier and better.

First, let me show you the numbers. This is the average roll for multiple d20s. The graph is form the same link above:


1d20: 10.5.
2d20, pick highest: 13.82
3d20, pick highest: 15.49
4d20, pick highest: 16.48
5d20, pick highest: 17.15
6d20, pick highest: 17.62...

Did you notice a pattern here? When you have 2 advantages, you gain a bonus of roughly +2 to your average when compared to one advantage. With 3 advantages, the bonus is close to +3. You can say you get a +4 bonus if you have 4 advantages, but that is pushing it, and the system breaks after the fifth advantage. But I reckon having five or more advantages at once will be very rare indeed...

To make it short:

If you have more than one advantage, roll two dice and pick the highest as usual, but add the total number of advantages to the result: +2 if you have 2 advantages, +3 if you have three, and +4 if you have four or more.

I like this system both because advantages get progressively less meaningful, and because having a second advantage is still a significant (+2) bonus, specially against high DCs. Two advantages, in fact, is the most common "problem" this rule is trying to fix: since you can often get one from your character sheet (which shouldn't be the entirety of your character IMO), it is nice to be able to get a second one through tactics, circumstances, and so on.


  1. The whole point of the mechanic is to avoid using bonuses and maluses so I am not sure your fix is a good one. I smply give a "normal" advantage or disadvantage by very roughly comparing the number of factors giving advantages and disadvantages.

  2. Ignoring for one moment the fact 5e was 'suppose' to be a balancing of all prior versions, stacking Dis/Adv is a surefire way of killing off the 'younger' player builds and also a gateway for B.S.-stacking 'unfallible' successes without skewing AC/DC on certain checks by the DM/GM.

    I would suggest a hybrid that all rolls are made - Adv/Dis - and then for each highest-Adv/lowest-Dis face value cancels each other out (and like with Death Saves, Crit-20 and Nat-1 double the Adv/Dis they account for). Then you +2/-2 the face value of the appropriate die by each Adv/Dis that remains by the amount of dice remaining.

    To simulate the mess above for easier visual, consider this: Rolling 5Adv and 2Dis. The numbers come out to be 19, 16, 16, 14, 13, 5, and a Nat-1. By what I stated above, Nat-1 counts for 2 Disadvantage rolls. So, The 19 & first 16 is canceled out by the Nat-1; and the other 16 is canceled by the last Dis roll of 5. That makes the roll of 14 and the other roll becoming a +2, so a 16.

    This could be improved upon I know, though since this takes into consideration of cumulative Crits/Nats, like with how the OP and who was linked to suggests, this is homebrew ruling; that means it's not RAW or RAI that have any say in the matter, ultimately it is the DM/GM that truly has the final say: their story, their ruling. Though since I am not narrating for a 'war-game' campaign and it is more for just having fun, my twist on Adv/Dis works just fine for the players that occasionally (but not intentionally) find themselves with in auch a situation.

  3. I've calculated the analytical functions of these probabilities. See if you find that useful.